[Cob] How warm must it be to work?

[Shannon C. Dealy]

On Mon, 25 Oct 2004, Amanda Peck wrote:

[snip]
> types are much nicer, both for the cats and for me--but it doesn't separate
> into slip if the bottom layers stay in liquid too long.  So I'd guess it
> either has some gypsum in it, or else is a very low-fired clay.
[snip]

Bentonite is rather different from most clays that people work with
because it absorbs and holds far more water (which is why it is used for
cat litter), and it is sometimes used as a sealant.  If you put bentonite
in a bucket, add water and let it sit, the top of the clay will seal the
water out of the bottom of it (the moisture will seep in, but very slowly)
and form a very solid plug at the bottom of your bucket making it very
difficult to mix.  To make a clay slip, you normally mix water and clay,
but the clay (any clay) will eventually settle out (hours, days, weeks,
or even months depending on the clay), you have to mix it up to get it
back into suspension, bentonite is generally alot harder to mix once it
is out of suspension.  I usually measure the water first, then add the
clay slowly while mixing to prevent this problem.  To give you an idea of
how absorbent it is, one pint of bentonite can soak up roughly a gallon of
water.

Shannon C. Dealy      |               DeaTech Research Inc.
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